1. Field of the Invention
This invention relates to thermal engines having power sources external or internal to their cylinders, such as, for example, Stirling cycle or compressor-type engines.
2. Description of Pertinent Information
Thermal engines have been designed with their power sources located externally or internally to their cylinders. For example, one type of thermal engine has pistons that reciprocate in linearly arranged cylinders. Appropriate connecting rod assemblies and seals are associated with this type of engine. Another type of thermal internal combustion engine uses opposed pistons travelling alternating linear trajectories in a polygonally-shaped engine, such as disclosed in French Pat. No. 1,176,758. This polygonal type of engine is more well-known by the name "Delta" engine. Still another type of thermal engine is a toroidal cylinder engine having orbital pistons in which thermal cycle phases are obtained by direct uncovering of exhaust ports on the pistons' trajectories. This type of engine is equipped with rotating port closures subject to rapid and intermittent actuation by a cam, as disclosed in French Pat. No. 1,432,977.
Three other types of thermal engines with power sources external or internal to their cylinders have been developed. Toroidal internal combustion engines use pistons that are subject to centrifugal forces and move in a circular path and transmit an alternate circular movement to an oscillating lever drive shaft, as disclosed in French Pat. No. 2,003,286. Rotating pistons of the epitrochoidal type have two stage operating characteristics, such as disclosed in French Pat. No. 2,037,381. Finally, Stirling cycle engines have been developed in which pistons reciprocate in linearly-aligned cylinders and are attached to rhomboidally-shaped connecting rod assemblies attached to crankshafts. Engine sealing is accomplished by means of a rolling skirt and counterpressure. In addition, Stirling cycle engines comprising four cylinders of a barrel type having double-effect pistons actuating guide blocks that function as a simplified crankshaft have been developed.
Engines with external or internal power sources, the most characteristic of which have been described above, suffer from a variety of disadvantages. First, these are frictional losses inherent in the kinematics of these engines due to the large trajectory of their components. Second, frictional forces arise at a large distance from the rotational axis of many components. The intensity of these frictional forces is increased by centrifugal forces of the moving components and by the movement of components arising from the thrust of gases in the engine. Third, problems exist with the dynamic tolerances among components in which reciprocating or angular movement with respect to each other is comparatively great. In addition to these disadvantages, Stirling cycle engines present problems due to variations in power output. Power variations are caused by injection of a fuel, e.g., hydrogen, at the beginning of isothermal compression by means of a very sensitive, high pressure distributor.
Stirling cycle engines have chambers that together with their associated pistons form a "hot side" of the piston or hot gas phase "envelope" and a "cold side" of the piston or cold gas phase "envelope". Hot and cold sides or envelopes are connected by connecting means comprising a thermal accumulator or regenerator, a cold source, and a heat source. Gas alternately traverses the cold and hot envelopes.
In these Stirling cycle engines, problems can occur due to load losses resulting from the complexity of the connections between the hot and cold sides or envelopes. For each connecting two envelopes or sides, the arrangement of the cylinders forms nests of boiler tubes having elements of various shapes and lengths lacking hydraulic equipotentiality and leading to different outputs.
Finally, the prior art thermal engines described above require the use of a great number of different mechanical parts that presents maintenance problems due to the difficulty in replacing hard-to-find parts.